In the paperboard industry, it is known to use lead edge sheet feeders for feeding sheets one at a time in timed sequence to downstream equipment, e.g. container blank processing machinery. Such lead edge feeders employ vacuum conveyors as, for example, disclosed in U.S. Pat. No. 4,494,745 and U.S. Pat. No. 4,867,433. These lead edge feeders include a pair of pull rolls for taking over feeding of each sheet from the initial vacuum conveyor and then feeding the sheet to the downstream equipment. Such pull rolls can have an adverse effect on the sheets gripped and fed therebetween.
It has been proposed to replace these pull rolls by a second vacuum conveyor as disclosed in U.S. Pat. Nos. 3,941,372 and 4,236,708 to avoid damage to the sheets by the pressure of the pull rolls, e.g. crushing of corrugated paperboard sheets.